The conformers of chloromethylmethyldifluorosilane studied by vibrational spectroscopy andab initio methods

摘要: Chloromethylmethyldifluorosilane (CH2ClCH3SiF2) was synthesized for the first time. Raman spectra of liquid were recorded at various temperatures between 298 and 175 K amorphous crystalline solids obtained. Infrared in vapour, solid phases MIR FIR regions. Additional compound isolated argon nitrogen matrices obtained 10 K. The chloromethylmethyldifluorosilane showed existence two conformers, anti gauche, present vapour liquid. By careful annealing formed by depositing on a cold Cu finger (Raman) or CsI silicon windows (infrared) 80 K, different crystals formed. One these, after to 125 (crystal I), contained conformer; other, achieved ca 170 II), molecules gauche conformation. If cooled, crystal II formed, suggesting this be stable, whereas I appeared metastable. conformers had approximately same enthalpy liquid, giving negligible ΔH (gauche–anti) equal 0.2 ± 0.4 kJ mol−1, but conformer stable II. Intensity variations matrix indicated that low-enthalpy both probably also vapour. These experimental data make very reliable assignment bands possible. Ab initio calculations performed HF/6–311G* level, from which optimized geometries, infrared intensities scaled vibrational wavenumbers conformational energy derived 5.9 with being low-energy conformer. Copyright © 2000 John Wiley & Sons, Ltd.